[PGO] Function section hotness prefix should look at all blocks

Summary:
The function section prefix for PGO based layout (e.g. hot/unlikely)
should look at the hotness of all blocks not just the entry BB.
A function with a cold entry but a very hot loop should be placed in the
hot section, for example, so that it is located close to other hot
functions it may call. For SamplePGO it was already looking at the
branch weights on calls, and I made that code conditional on whether
this is SamplePGO since it was essentially a noop for instrumentation
PGO anyway.

Reviewers: davidxl

Subscribers: eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D41395

llvm-svn: 321197

1 files changed, 4 insertions, 11 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index afe1cedb9e3..d6f55bba716 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -352,8 +352,6 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
   // Clear per function information.
   InsertedInsts.clear();
   PromotedInsts.clear();
-  BFI.reset();
-  BPI.reset();
 
   ModifiedDT = false;
   if (auto *TPC = getAnalysisIfAvailable<TargetPassConfig>()) {
@@ -365,14 +363,16 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
   TLInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
   TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
   LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+  BPI.reset(new BranchProbabilityInfo(F, *LI));
+  BFI.reset(new BlockFrequencyInfo(F, *BPI, *LI));
   OptSize = F.optForSize();
 
   ProfileSummaryInfo *PSI =
       getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
   if (ProfileGuidedSectionPrefix) {
-    if (PSI->isFunctionHotInCallGraph(&F))
+    if (PSI->isFunctionHotInCallGraph(&F, *BFI))
       F.setSectionPrefix(".hot");
-    else if (PSI->isFunctionColdInCallGraph(&F))
+    else if (PSI->isFunctionColdInCallGraph(&F, *BFI))
       F.setSectionPrefix(".unlikely");
   }
 
@@ -652,13 +652,6 @@ bool CodeGenPrepare::isMergingEmptyBlockProfitable(BasicBlock *BB,
   if (SameIncomingValueBBs.count(Pred))
     return true;
 
-  if (!BFI) {
-    Function &F = *BB->getParent();
-    LoopInfo LI{DominatorTree(F)};
-    BPI.reset(new BranchProbabilityInfo(F, LI));
-    BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
-  }
-
   BlockFrequency PredFreq = BFI->getBlockFreq(Pred);
   BlockFrequency BBFreq = BFI->getBlockFreq(BB);